BACILLUS ANTHRACIS 



373 



length. Occasionally filaments 20 to 25 microns in length are 

 observed, which exhibit no demonstrable septation; these long rods 

 may be single cells or chains of cells in which septation is imper- 

 fect. The ends of the bacilli are square cut and often appear 

 to be concave, particularly when the organisms are examined in a 

 strained preparation made directly from the blood of an infected 

 animal. Occasionally the ends are somewhat thickened, giving the 

 bacillus an appearance which suggests a segment of bamboo. Bacillus 

 anthracis produces short chains of three to eight elements in the 

 bloodvessels of infected animals, and in artificial media it produces 

 long, coiled chains of bacilli which give a characteristic filamentous 

 appearance to the colonies upon solid media. The organism is non- 

 motile, and possesses no flagella. A capsule 1 is formed around the 



FIG. 52. Bacillus anthracis, spore formation. X 1000. (Giinther.) 



bacilli in the animal body and also in cultures containing albuminous 

 substances, as uncoagulated blood serum. 2 Spores are produced in 

 media freely exposed to the air between the temperatures of 15 C. and 

 40 C. The lower limit of spore formation has a practical bearing 

 upon the presence of anthrax spores in soil. In the temperate zones 

 a temperature exceeding 15 C. in midsummer is not found at depths 

 greater than five feet, hence anthrax carcasses buried deeply are not 

 likely to cause infection of the soil. It has been stated that earthworms 

 may carry infected material from the deeper layers of the soil to the 



1 The capsule was first seen by Serafini (Progresso Medico, 1888), but Johne (Deutsch. 

 Ztschr. f. Tiermed. u. vergl. Path., 1893, xix, 244; 1894, xx, 426) first called attention 

 to the diagnostic importance of the capsule in the diagnosis of anthrax of the domestic 

 animals. 



2 Haase, Deutsch. Ztschr. f. Tiermed. u. vergl. Path., 1894, xx, 429; Johne, ibid., 

 1894, xxi, 142. 



